Evaluate the function by using the Riemann sum

Consider the function

I need to calculate by using the definition of Riemann sum for - right end-points,

so, I started by finding

after that

so, I'm basically asked to provide

as a function of n, without summation symbols, and for this I entered step i) , but it was considered as wrong, so obviously, my mistake is somewhere above,

, here I obtained , but it is actually wrong since all my work-up before is wrong,

can you, please help me with this,

thanks,

dokrbb

Re: Evaluate the function by using the Riemann sum

Quote:

Originally Posted by

**dokrbb** Consider the function

I need to calculate

by using the definition of Riemann sum for

- right end-points,

so, I started by finding

after that

I'll stop you here, first of all, your counter in your sum is "i", not "n", so they should all look like

I'll stop you here too. After this point, you are actually evaluating the sum and getting a closed expression for it. You should NOT continue to put in the summation signs as you aren't going to be summing anything after this point...

Quote:

so, I'm basically asked to provide

as a function of n, without summation symbols,

and for this I entered step i) , but it was considered as wrong, so obviously, my mistake is somewhere above,

, here I obtained

, but it is actually wrong since all my work-up before is wrong,

can you, please help me with this,

thanks,

dokrbb

So once you have fixed everything, you should have

which you can now simplify as much as you like :)

Re: Evaluate the function by using the Riemann sum

Quote:

Originally Posted by

**Prove It** I'll stop you here, first of all, your counter in your sum is "i", not "n", so they should all look like

I'll stop you here too. After this point, you are actually evaluating the sum and getting a closed expression for it. You should NOT continue to put in the summation signs as you aren't going to be summing anything after this point...

So once you have fixed everything, you should have

which you can now simplify as much as you like :)

and what about my lim at infinity?

Re: Evaluate the function by using the Riemann sum

Quote:

Originally Posted by

**dokrbb** and what about my lim at infinity?

Well, have you tried simplifying? You should easily be able to see what the limit is after simplifying...

Re: Evaluate the function by using the Riemann sum

Quote:

Originally Posted by

**Prove It** Well, have you tried simplifying? You should easily be able to see what the limit is after simplifying...

actually that's my problem - I got the same result as you showed me, well just it needs to be written without summation symbol, but after simplifying it, I have got -(9/2), which is not correct, I checked my steps, and got another example (-36/2) = -18, but it's again not what it's expected,

can you just show me these few steps, I have got a dozen of pages with corrections and simplifications, and have no idea which one to put here in order to show you that I really tried this exercise,

Re: Evaluate the function by using the Riemann sum

Start by expanding everything and then dividing top and bottom by the highest power of n.

Re: Evaluate the function by using the Riemann sum

Re: Evaluate the function by using the Riemann sum

Re: Evaluate the function by using the Riemann sum

Quote:

Originally Posted by

**FelixFelicis28** The issue is your

, you've evaluated the limit correctly.

I haven't looked through your working to pinpoint an error, but I make

.

Now let

and it should give

which I believe is correct.

it is, indeed, correct,

so I was just loosing this at the end of my evaluation, because of keeping separately through all the steps?

thanks a lot,

dokrbb